Genetic counseling: Craniosynostosis-1
Craniosynostosis Overview *Craniosynostosis refers to the premature fusion of the cranial sutures (growth centers between the bones of the skull) *The skull is made up of a number of bones and when those bones fuse together too soon it doesn't allow the head to grow in the usual fashion and can lead to changes in head shape *Usually cranial sutures do not fuse completely until the fourth decade Primary vs. secondary craniosynostosis *Primary *suture growth is altered *head frequently assymmetric *the brain continues to grow in areas where sutures are open *most individuals are normal neurologically *benefit from surgery *Secondary *growth of brain is impaired *neurologically abnormal usually Isolated vs. Syndromic *Isolated *usually presents during first year of life *usually involves only one cranial suture (may involve more than one though) *no other associated abnormalities except those produced secondarily as a result of premature fusion of suture *sagittal suture is most common site for isolated craniosynostosis *suture that runs from front to back and separates parietal bones *results in head elongated from front to back due to limited growth laterally (scaphocephaly) *intracranial pressure is usually in the normal range *cranial surgery usually recommended to give a more usual head shape *usually babies with isolated craniosynostosis grow and develop normally *Syndromic *Other characteristic features present *over 60 syndromes described with craniosynostosis as a feature *bicoronal synostosis is the type present in the most common syndromes *Most follow AD inheritance *Most individuals with a craniosynostosis syndrome have normal intelligence *Saethre-Chotzen syndrome is the most common *characterized by facial asymmetry, low frontal hairline, ptosis, deviated nasal septum, brachydactyly, and partial cutaneous syndactyly of the toes *Crouzon - next most common (1 in 25,000 live births) *characterized by maxillary hypoplasia, shallow orbits, and ocular proptosis *Apert syndrome *characterized by strabismus, maxillary hypoplasia *complete symmetrical syndactyly of hands and feet *associated with risk for developmental delay (unlike most of the other AD craniosynostosis syndromes) *Pfeiffer syndrome *maxillary hypoplasia *broad thumbs and big toes *mild cutaneous syndactyly Incidence of isolated nonsyndromic craniosynostosis *0.4-0.6 per 1000 births *so about 1 in 2000 births (Fetology, 2000) Recurrence risks for isolated nonsyndromic craniosynostosis *usually sporadic *genetic basis not discovered except for certain cases of unicoronal synostosis *In study of 125 patients with craniosynostosis only 2.5% of those with isolated synostosis had positive family history *patients with isolated craniosynostosis and a negative family history are not believed to have an increased incidence of recurrence above the background Ultrasound detection of craniosynostosis *difficult to detect on ultrasound *when it is detected it is often not until 3rd trimester *sometimes features associated with syndrome are detected on ultrasound (fused digits etc) Surgery *objective is to allow adequate brain growth and imporve appearance *Surgery for isolated craniosynostosis is usually a single operation and produces excellent cosmetic results in 93% References *Bianchi, DW, Crombleholme, TM, and D'alton, ME. Fetology: Diagnosis and management of the fetal patient. McGraw-Hill. 2000. *http://www.worldcf.org/cran_3a.html - simple definitions of types of craniosynostosis *http://www.erlanger.org/craniofacial/book/craniosynostosis/cranio_2.htm - great pictures and explanations of the types of craniosynostosis *http://www.hopkinsmedicine.org/craniofacial/LynmProject/DS/DSSV/SV0.HTM - description and types of craniosynostosis Notes The information in this outline was last updated in 2003. Material obtained under GFDL Licence from http://en.wikibooks.org/wiki/Handbook_of_Genetic_Counseling